UEFA Champions League 2013: Stars to Watch in Remaining Round of 16 Matches

Four matches remain to complete the first leg in the Champions League Round of 16. Several top contenders, including Spanish powerhouse Barcelona and last season's runner-up Bayern Munich, are still waiting to begin the knockout phase.

After watching the first four games, it's easy to understand why the Champions League attracts so much worldwide attention. The level of play is higher, the star power is amazing and the intensity from clubs across Europe is through the roof.

That should continue when the action picks back up next week. So let's take a look at some of the key attacking players that will be in action on Feb. 19 and 20.

Theo Walcott (Arsenal)

Arsenal understand they will have to score in order to keep pace with Bayern Munich. The Bundesliga leaders have scored eight goals more than any other club in league play and found the net 15 times in six matches during the UCL group stage.

To counter, the Gunners will turn to Walcott. The 23-year-old forward got off to a bit of a slow start, but a hat-trick against Reading back in October seemed to get him going, and he's been one of Arsenal's most reliable players ever since.

The first leg is a home match for the Gunners, so they must focus on getting a result. That means Walcott, along with Olivier Giroud and Santi Cazorla, have to control the pace.

When Walcott does get a chance, he needs to convert. There's no margin for error.

Lionel Messi (Barcelona)

It takes a special player to move us beyond amazement.

At this point, no matter what stats somebody rattles off about Messi, they're believable because he's accomplished so much with Barcelona. Nothing he does is shocking because he makes it look so easy.

Barca, one of the tournament favorites, begin their journey toward the Champions League final with a matchup against AC Milan. It's one of the premier battles of the Round of 16, and Barcelona will lean heavily on their star striker.

He was on fire during the group stage, tallying five goals and two assists in six matches. You would think the immense pressure would cause him to falter eventually, but he handles it all in stride and fans should expect nothing different against Milan.

Jackson Martinez (Porto)

Martinez is a player who flies below the radar. The Colombia international has a tremendous finishing instinct in the final third and has embraced his role since joining Porto over the summer. He scored three goals in group play.

Even more impressive is his recent form. Martinez has scored at least one goal in nine straight matches heading into the club's league match against Beira Mar. It's something Malaga, Porto's Round of 16 opponent, is surely aware of.

Whenever a player is playing that well, it makes a club extremely dangerous in a tournament format. If he can maintain his current form, Porto quickly become a tough opponent instead of an afterthought. Martinez hopes he can prove that starting on Tuesday.